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The quantum trick that can help you live a better life – probably

Quantum theory suggests everything that can happen, does. Now a phone app gives us a way to exploit this weirdness – and enjoy the best of all possible worlds

Sharmelan Murugiah

By Philip Ball

MINCE pie or another slice of Christmas cake? If you’re having trouble deciding, perhaps you need the Universe Splitter. Type the choices confronting you into this handy app and it promises to contact “a laboratory in Geneva” that will conduct an experiment to tell you which decision to make.

The app’s guarantee is that, whatever the best choice might be, you will get to enjoy it for sure – if not in this world, then as another you in a parallel one. Sink back into your armchair, pour a brandy (or sherry?) and prepare to have your mind split apart. We are about to enter the quantum realm – home, perhaps, to many worlds where you can have your cake, and pie, and eat both. Or can you?

The origins of this agreeable suggestion lie in a city famed for its sweetmeats: Vienna, Austria. In the early 1920s, physicist Erwin Schrödinger was seeking an equation that could explain the workings of quantum particles – things like photons and the tiniest building blocks of the matter that makes up you, me, your armchair and that plate of Christmas cake.

In 1925, Schrödinger found his equation, which indicated that everything there is to know about a quantum particle was described by a rather mysterious mathematical entity called a wave function. A year later, German physicist Max Born argued that this wave function supplied you with the probability of finding a quantum particle at a point in space, if you performed some experiment to measure it. As long as you didn’t measure it, this position was somehow indefinable, …